[erlang-questions] Is Erlang a good tool for this particular project?

Joseph Norton norton@REDACTED
Wed Jul 13 16:07:46 CEST 2011

Matt -

There is already a client and server implementation similar to your idea that uses JSON as the wire format over TCP/IP.  See the section "JSF" for a brief description:


Download and build instructions are here:


Hope you find it helpful.

- Joe N.

On Jul 13, 2011, at 9:42 PM, Matthew Hillsborough wrote:

> Hi Ale and everyone else who replied,
> That's exactly the point, I don't think HTTP is necessary at all! There is the overhead of sending extraneous HTTP headers over the wire. All of those additional bits take additional CPU time and bandwidth (on a mobile device with limited CPU and even more limited bandwidth!). I see absolutely no need for sending HTTP headers and parsing them from the response for this, particularly because I am not building a web browser based application. I have access to C/C++/Objective-C (on iOS) and Java (on Android) and these are perfectly capable of working with TCP sockets. A friend of mine suggested that I just pass messages to the server as JSON using a prefixed header that specifies the length of the message. That would be it! Simple and compact. 
> I just wanted to validate the idea and see if others thing I'll run into too many edge cases uses TCP sockets via an RPC type server to build this server/client architecture out. I want to really make it reusable so all of my mobile products can use it. 
> Loving all the advice coming in! Thanks all.
> Matthew. 
> On Tue, Jul 12, 2011 at 5:03 PM, Ale <peralta.alejandro@REDACTED> wrote:
> Hi,
> Just a thought here... Erlang is great for scalability and handling
> multiple connections, and well I'm sure a lot of people can give you a
> better description fo this, but it occurred to me if you considered
> other protocols instead of HTTP? The problem seems to be there rather
> than the language you write your sever. It occurred to me that you
> might benefit from using Jabber/XMPP. Googling I found some iOS jabber
> clients http://code.google.com/p/xmppframework/ and the cannonical
> jabber server is written in Erlang.
> Regards,
> 2011/7/12 Matthew Hillsborough <matthew.hillsborough@REDACTED>:
> > Greetings Erlang community,
> > Let me further elaborate on my question that's in the subject of this
> > message. I tried to reach out with this question on StackOverflow, however I
> > did not have much luck there. Perhaps the community here can provide some
> > feedback here for me to let me know if I'm on the right track or if Erlang
> > is not the right tool for what I'm trying to accomplish.
> >
> > I'm building native mobile applications in both iOS and Android. These apps
> > require "realtime" updates from and to the server, same as many (but not
> > all) network-based application does (Facebook, social games like Words with
> > Friends, Finance applications, etc). The communication here is
> > bi-directional, in the sense that the server might have updates for the
> > mobile clients and the clients will be pushing data down to the server
> > whenever necessary.
> >
> > I think using HTTP long polling for this is over kill in the sense that long
> > polling can be detrimental to battery life, especially with a lot of TCP
> > setup/teardown for every HTTP connection the device needs to send out
> > through the wire. It might make sense to have the mobile applications use
> > persistent TCP sockets to establish a connection to the server, and send RPC
> > style commands to the server for all web service communication. This
> > ofcourse, would require a server to handle the long-lived TCP connection and
> > be able to speak to a web service once it makes sense of the data passed
> > down the TCP pipe. I'm thinking of passing data in plain text using JSON or
> > XML and then using some kind of Erlang interface to HTTP to call a web
> > service to handle all the REST type communication. The responses would then
> > go back to the "RPC" Erlang instance, which would send the updates to the
> > appropriate client(s).
> >
> > Perhaps an Erlang based RPC server would do well for a network based
> > application like this. It would allow for the mobile apps to send and
> > receive data from the server all over one connection without multiple
> > setup/tear down that individual HTTP requests would do. Since no web browser
> > is involved, we do not need to deal with the nuances of HTTP long-polling at
> > the mobile client level. I also haven't seen great long polling/keep-alive
> > support on the client-side in iOS, but that's irrelevant for the community
> > here.
> >
> > A lot of these "COMET" and long-polling/streaming servers are built with
> > HTTP in mind. I'm thinking just using a plain-text protocol over TCP is
> > better catered for the type of app I'm building, will make the client more
> > responsive, allow for receiving of updates from the server without
> > constantly polling the server, etc.
> >
> > I also looked into HTTP pipelining, but it doesn't look to be worth the
> > trouble when it comes to implementing it on the clients. Also, I'm not sure
> > if it would allow for bi-directional communication in the client<->server
> > communication channel.
> >
> > Am I completely out of line in thinking that building a custom solution in
> > Erlang is a good idea here? To my understanding, Erlang excels at servers
> > like this, and if I run the server on tcp/80, I should be able to avoid most
> > firewall/port issues. The client would need work to deal with timeouts, re
> > connections, acknowledging receipt of asynchronous requests, but that's not
> > Erlang's problem.
> >
> > Has anyone built something similar before? Should I just stick to a web
> > server and deal with "COMET" type technologies? (WebSockets, long-polling,
> > client-side polling).
> >
> > Was hoping someone could solidify that I'm not entirely insane for wanting a
> > better solution than HTTP would serve in this case, at least at the client
> > level. I'll still be using HTTP/REST extensively, the Erlang server would
> > just handle the persistent connections and messaging to the Web Service
> > (which would probably be something like Django or Rails).
> >
> > Sorry for the long post; I am just excited to get into the heads of people
> > who are smarter than I.
> >
> > Happy hacking!
> >
> > Matthew
> >
> > _______________________________________________
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> >
> >
> --
> Ale.
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Joseph Norton

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